.four .shape.a {
    left: calc(50% - 8em);
    animation: four 6s infinite cubic-bezier(.57,-0.5,.43,1.53);
}
.four .shape.b {
    left: calc(50% + 8em);
    animation: four 6s infinite steps(1)
}
@keyframes four {
    0%, 10% {
        transform: none;
    }
    26%, 30% {
        transform: rotateZ(-45deg) scale(1.25)
    }
    40% {
        transform: rotateZ(-45deg) translate(2em, -2em) scale(1.8)
    }
    50%, 74% {
        transform: rotateZ(-45deg) scale(1.1)
    }
    90%, 100% {
        transform: none;
    }
}